Accumulator



March 6, 1962 P. H. TAYLOR 3,023,786

ACCUMULATOR Filed Feb. 10, 1954 2 Sheets-Sheet 1 March 6, 1962 P. H. TAYLoR 3,023,786

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United States Patent G 3,023,786 ACCUMULATOR Paul Hollis Taylor, Grand Island, N.Y., assignor to Tayco Development, Inc., Tonawanda, N.Y., a corporation of New York Filed Feb. 10, 1954, Ser. No. 409,341 9 Claims. (Cl. 13S-31) This invention relates to hydraulic accumulator energy storage devices and more particularly to a hydraulic accumulator which utilizes as an energy storage medium the constant pressure range of the polymorphic transition of ymaterials under pressure from one state to another.

Hydraulic systems based on liquids as on incompressible power transmission medium depend upon accumulators for peak demand and pressure leveling conditions. ln use liquid is pumped against a resilient energy storage medium in the accumulator such as tree Weights, springs, compressed gas or gas loaded pistons or diaphragms. The cheapest and most eicient apparatus spacewise and weightwise consists of the gas charged accumulator against which liquid is pumped for energy storage. Preterably a Ithin diaphragm separates the gas from the liquid to prevent gas loss through aeration. The operating disadvantage of the existing accumulators is in the Wide pressure differential between fully charged and the discharged volumes of the accumulator. For instance, in a 3,000 p.s.i. 71/2 spherical accumulator with an air charge of 2,000 p.s.i. the hydraulic pressure varies between 3,000 and 2,000 p.s.i. over the 64 cubic Iinch discharge of the 176 cubic inch total accumulator volume. lt will thus be obvious that the force response of any hydraulic servo operating from that storage system varies over 1/3 through the discharge of the energy storage medium. This variation atects the operation of valves, servos and other pressure sensitive devices in the system. While this can be corrected by using a pressure regulator, it is obvious that the regulator adds weight and space and cuts down the mechanical elciency because it must be set for the lowest discharge pressure of 2,000 p.s.i.

This would result in a work output loss of 32,000 in. lb. or the diiference between the 160,000 in. lb. for the unregulated accumulator discharge against the 128,000 in. lb. for the regulated discharged. It is also apparent that the accumulator and related apparatus must be designed for the maximum structural requirements even though it operates only at these pressures for a brief part of its operation.

Aside from the operating dhiiculties, hydra-pneumatic accumulators present great installation and maintenance difficulties in that leakage of the gas or air charge is always possible which requires high pressure tanks or pumps for periodically servicing or charging the accumulators. The separate filler port and valve by which the high pressure gas is introduced within the accumulator is another source of failure. Because of the substantial volumes reduction a slight leakage rapidly reduces the gas to the point where the accumulator is unworkable. In military use, such as for guided missiles and aircraft, this increases the logistics requirements and presents another possible military emergency. Failure to have stored gas or gas pressurizing equipment at the front renders the equipment unserviceable.

Hydra-pneumatic accumulators also present a possible hazard in that in the event of fracture of the accumulator shell the great expansive power of the gas charge due to its extreme volume reduction at the high pressures presents a serious fragmentation and personnel hazard problem. This is particularly critical in military equipment where a hit on an accumulator may result in its fragmentation and greater damage to personnel than "ice that from direct enemy action. This is heightened by the inherent bulk of accumulators which also makes them vulnerable The principal objects of this accumulator are to provide:

(a) reduction in Weight, size and costs for a given energy output;

(b) constant pressure within its output range, and;

(c) improved structure through constant stress characteristics.

The objects of this accumulator with respect to military applications are to provide:

(a) (b) (C) (d) (e) (f) FEGURE l is an axial section of an accumulator constructed according to one embodiment of my invention and illustrating the high and low pressure components in the fully charged condition.

FIGURE Z is a cross section taken as noted along line 2-2 of FIGURE l.

FIGURE 3 is an axial section'of a modied embodiment of my accumulator for medium pressure applications.

FIGURE 4 is an axial section of an embodiment of my invention similar to FGURE 3 except in the more efcient spherical shape.

FlGURE 5 is a graph illustrating the characteristics of the energy storage materials Vthrough the polymorphic transition period used in my accumulators.

FIGURE 1 illustrates the preferred embodiment of my invention for high efficiency requirements such as for aircraft and guided missiles where Weight and space must be minimum. Accumulator 20 has an ultra high pressure (42,600 psi.) chamber 30 adapted to contain a material such as liquids or solids in the ultra high compressibility range. A low pressure (3,000 p.s.i.) chamber 40 is provided utilizing liquids in their essentially incompressible range. Both chambers, however, may for instance be filled with the same hydraulic liquid except that because of the pressure dilerential the Same liquid can be considered as both imcompressible and compressible in the same system. Preferably, however, for maX- imum eciency a material should be used which has a comparatively low pressure polymorphic transition to provide constant pressure as will be discussed hereinafter. This material may in some instances be liquid, however, in this maximum efficiency accumulator I prefer to use a crystal salt material 32 (silver iodide). This is acted upon by a small high pressure piston 34 'which is direct-ly coupled to a large low pressure piston 41 by means of its attachment to the reduced shank 34a and shoulder 34b by nut 43. A suitable seal 42 seals piston 41 in loiv pressure chamber 40. High pressure piston 34 is sealed by the high pressure female seal 36 which is retained by nut 37 in end 3S of chamber 30. A tubular diaphragm 31 is retained at shoulder 38a by lip 31a.. While diaphragm 31 could be dispensed with it is desirable to contain a liquid 33 by which pressure can be transmitted to crystals 32 Without the friction losses from piston 34 operating directly on the crystals. Caps 38 and 39 forming the high pressure chamber 30 are preferably cup shaped and brazed or welded in place to avoid the notch eect ot threads. However, the low pressure chamber 40 is preferably capped by the threaded cap 23 and seal 22 for a purpose to be discussed hereinafter.. Threaded reduction in target size and vulnerability to gunfire; elimination of fragmentation;

charging by the iluid source;

elimination of gas, and;

supply problem for a military force in the iield; reducing the logistics requirements.

boss 24 serves as the attachment for the ared hydraulic tubing 2-5 from the System.

Material 32 (silver iodide) was chosen for the resilient pressure medium because of its large volume decrement of 16.3% through the polymorphic transition. This material compresses at a constant pressure of 42,600 p.s.i. from .011 reduction in volu-me to .174 or a 16.3% reduction in volume at constant pressure of 42,600 p.s.i. as is shown in lFIGURE 5 as curve X. 'This means that 3 cubic inches of silver iodide AgI will provide the same energy output of 64 cubic inches in the hydra-pneumatic accumulator previously discussed and requires a total of only 18.4 cubic inches to be the equivalent of the 176 cubic inches of the hydra-pneumatic accumulator for the same work. Obviously, however, 64 cubic inches of low pressure hydraulic liquid will still be required for the low pressure chamber 40 so the total savings in volume is 17'6-(64-I-l8.4) :93.6 cubic inches of volume or 1/2 the volume of the present equivalent accumulators. However, since the silver iodide weighs 5 times the liquid, the Weight reduction is vapproximately a third of the equivalent accumulators.

It should be obvious that for military requirements the target area of any accumulator is much less and the smaller curved surface more readily deflects Vbullets or shrapnel. In. addition, the thicker walls of the high pressure' chamber cannot be penetrated. Since -a solid is used ast-he compressible `medium and at maximum it is compressed only 17% by volume instead of the 200 times reductionV in volume of the gas of the hydra-pneumatic 'accumulator that in the event of fracture slight leakage relieves all fragmentation force thus making this accumulator safer in military equipment.

Ease of -charging is another important factor for Whereas hydra-pneumatic accumulators must be serviced by high pressure pneumatic systems or tanked gas, here we are dealing only with an initial precharge or compression Y of .011 by volume which can easily be achieved mechanically as follows:

Place chamber 4l) upright and with chamber 30 filled, diaphragm 31 and seal 36 are put in place and diaphragm 31 is filled with liquid 33 to the top of seal 36. Piston 34 is placed inside seal 36 yand cap 23 is placed over piston 41. Piston 34 is then forced into seal 36 mechanically -by a push rod inserted through 4fitting 24 pressing on piston end 34a from a hydraulic or arbor press to achieve the .011 compression. Cap 23 is then threadedly engaged to chamber 40 to hold piston assembly 34-41 in place. When the low pressure hydraulic fluid from the pump Venters chamber 40 it forces piston 41 to the position of FIGURE l storing energy at constant prcsure because material 32 is pressurized to its polymorphic transition for the silver iodide crystals AgI (32) in charnber 30.

FIGURE 3 illustrates a modied accumulator 50 which is efficient for commercial installation in that it is cheaper and smaller than hydra-pneumatic accumulators but of approximately the same weight. This unit utilizes the lower pressure 8,000 p.s.i. polymorphic transition of ammonium iodide NH4I or some of the dimethyl silicones or similar behaving materials. Since commercial installations now run at these pressures no high low pressure differential is required. It will thus be observed that accumulator 50 can be made simply with a tube 51 and two welded or brazed ends 52 and S3 which are attached separately to insure a good joint in each end. Ammonium iodide crystals `60 are used and a exible tubular diaphragm 56 is optional, depending upon the position of the accumulator. If the plug end 53 can be maintained upright, the heavier specific `gravity of ammonium iodide will keep them in place without a diaphragm. Since ammonium iodide begins its transition at 8,000 p.s.i. at a volume decrement of only .003 or .3% it will be seen that it almost instantly is chargedy to 8,000 p.s.i. when hydraulic liquid lat that pressure enters at 57. Thereafter it will compress to a volume decrement of .143 or a 14% difference at a constant 8,000 p.s.i. It will be noted that all the gas valves of hydra-pneumatic accumulators are eliminated including the valve attached to the diaphragm to prevent its extrusion Aout of pipe S7. Because of the low initial ydecrement of volume to 8,000 p.s.i. it is obvious that nothting like this is required in this accumulator. While no weight saving is available in this unit over the hydrafpneumatic accumulator it still has military applications inthe smallest sizes where the complexity of the small hydra-pneumatic accumulator adds weight to miniatures. This is particularly true of small guided missiles.

FIGURE 4 illustrates the application of these principles to the familiar efficient spherical shape accumulator 80. In this conguration a liquid PXlene 100 is illustrated within the spherical shell 81. This liquid 100 also has an advantageous polymorphic transition at 8,000 p.s.i. and therefore can be used direct without step-down in a system. Its curve is shown as Y in FIGURE 5. To avoid -contamination of the hydraulic liquid of the system With PXlene 100 la separator piston 90 is used in bore 83 within sphere 81, although a diaphragm could be easily used. A two-way 93 integral nylon seal 92 is placed on piston 90. Piston 90 has a stop 95 for the fully loaded condition herein shown and a ball seal stop 96 on its other end for sealing against tapered tube end 98. A lip is formed integral on member 86 which is adapted to be brazed into sphere 81. Member S6 has a threaded attachment end 84 to which nut -97 attaches tube 97. An inverse tapered collar 99 reinforces tube 97 and fits tight within bore 83. Pressure on tube end 98 and collar 99 assists joint sealing. -A second auxiliary nylon seal 101 is also employed and is adapted to be clamped between end 84 and collar 99.

Having thus described .my invention and its advantages over the hydra-pneumatic accumulators due to the use of the compressibility of materials and particularly the constant pressure characteristics of materials in their polymorphic transition range it will be apparent that a basic new energy storage medium is provided which is not limited to the embodiments or materials described and claimed herein.

I claim:

1. An accumulator system comprising in combination container means, a non-gaseous material capable of reversible polymorphic transition disposed in saidcontainer means, and force transmitting mechanism operatively associated with said container means and said nongaseous material for causing polymorphic transition in said material to store energy in said accumulator, and force utilizing means operatively associated with said force transmitting mechanism for utilizing the energy released to perform work when said material undergoes reverse polymorphic transition.

2. An accumulator system comprising a closed chamber, a compressible material contained therein, said material being other than a lgas. and adapted for undergoing polymorphic transition at substantially constant pressure, hydraulic system means for subjecting said material to pressure at least equal to said constant pressure whereby energy of polymorphic transition is stored in said compressible material, and means for utilizing the energy of polymorphic transition released to perform work when the pressure on said material is reduced below said constant pressure.

3. An 'accumulator system comprising a casing having a chamber therein, a material other than a gas .disposed in said chamber', said material being adapted to undergo asubstantial reduction in volume at a substantially contant pressure to absorb energy and capable of releasing said energy when the pressure `on said material is reduced below said constant pressure, movable closure mechanism associated with and confining said materialr in said charnber, and energy transfer means operatively associated with said closure mechanism for compressing said material at or above said constant pressure to cause reduction in volume and for reducing the pressure on said material below said constant pressure and for utilizing the energy released from said material when the material volume increases.

4. An accumulator system comprising a closed chamber, a compressible non-gaseous material contained therein, said material being adapted for polymorphic transition with reduction in volume at substantially constant pressure, means for subjecting said material to a pressure at least as high as said constant pressure, force intensifying means associated with said pressure means, and a hydraulic system operatively associated with said force intensifying means yfor actuating the same to compress said material to said constant pressure to cause polymorphic transition, said hydraulic system being adapted for utilizing the energy `of polymorphic transition released when the pressure on said material is reduced below said constant pressure.

5. An accumulator system according to claim 4 wherein said pressure subjecting means and said force intensifying means comprise a composite piston having a relatively small piston area subjected to pressure from said material and a relatively large piston area subjected to pressure from said hydraulic system.

6. An accumulator system `comprising a casing having `a chamber therein, a material other than a gas disposed in said chamber, said material being adapted for reversible polymorphic transition at a substantially constant pressure, eXible means confining said material in said chamber, and a hydraulic system operatively associated with said exible means for exerting a pressure against the same at least equal to said constant pressure to cause polymorphic transition in said material and for absorbing the energy of polymorphic transition released when the pressure in the hydraulic system is reduced below said constant pressure.

7. An accumulator system according to claim 6 Wherein said exible means comprise a tubular diaphragm disposed in said chamber and having an open end connected to said hydraulic system.

8. An accumulator system comprising a casing having a generally spherical chamber therein, a tubular member disposed in said chamber .and having one end communieating with lthe chamber, a hydraulic system communicating with the other end of said tubular member, a piston shiftably disposed in said tubular member, and a cornpressible non-gaseous material capable of reversible polymorphc transition completely iilling said chamber and normally biasing said piston to said other end of said tubular member, whereby when the pressure in said hydraulic system exerted against said piston is equal to or greater than said constant pressure said piston compresses said non-gaseous material to cause polymorphic transition therein and when the pressure in said hydraulic system is reduced below said constant pressure said non-gaseous material undergoes reverse polymorphic transition to move said piston to perform Work in said hydraulic system.

9. An `accumulator system according to claim 8 wherein said piston includes a valve member at its end communicating with the hydraulic system, and valve seat means disposed 'at said yother end portion of said tubular member yadapted to coact with said valve member on said piston to seal said chamber when said valve member is disposed in said valve seat.

References Cited in the tile of this patent UNITED STATES PATENTS 2,321,093 Lupfer June 8, 1943 2,479,422 Shook Aug. 16, 1949 2,495,693 Byrd et al Jan. 31, 1950 2,523,964 Morris et al Sept. 26, 1950 OTHER REFERENCES Publication, Proceedings of the American Academy of Arts and Sciences, vol. 76, No. l, pages 2-7, February 1945.

Publication, Proceedings of the American Academy of Arts and Sciences, Vol. 76, No. 3, pages 71-87, March 1948.

Publication, Proceedings of the American Academy of Arts and Sciences, vol. 77, No. 4, pages 127-128, 131-134, February 1949.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIDN Patent. N0. 3,023,786 March 6, 1962 Paul Hollis Taylor fied that error appears n the above numbered pat- It is hereby certi and that the said Letters Patent should read as ent requiring correction corrected below.

Column 3, line 24, for "any" read my Signed and sealed this 11th day of September 1962.

(SEAL) Attest:

DAVID L. LADD ERNEST W. SWIDER Commissioner of Patents Attesting Officer 

